Process for producing paintable polymeric articles

ABSTRACT

A method for improving surface adhesion characteristics of a polymeric substrate and/or virgin polymeric material in which the portion of the surface of the polymeric substrate and/or virgin polymeric material to be treated is contacted with a composition containing at least one oxidizing agent. The oxidizing agent in the composition is present in a kinetically degrading state capable of producing at least one chemical intermediate which is reactive with the polymeric substrate/virgin polymeric material. Contact between the composition containing the oxidizing agent and the polymeric substrate/virgin polymeric material is maintained for an interval sufficient to produce or modify functional groups in the polymeric substrate/virgin polymeric material. The oxidizing agent of choice is a halogenated bivalent oxygen compound. The oxidizing agent is activated by an activator agent containing at least one carboxylic acid group or derivative thereof. The activator agent may be present in the composition upon initial contact with the polymeric substrate/virgin polymeric material, or may be added to the composition subsequent to initial contact with the polymeric substrate/virgin polymeric material.

BACKGROUND OF THE INVENTION

The present invention relates to a process for improving adhesioncharacteristics of a polymeric substrate surface and/or of a virginpolymeric material moldable into a substrate exhibiting improvedadhesion characteristics.

Polymeric materials provide excellent and versatile mechanical qualitiesand find use in a wide variety of applications. In certain instances, itis necessary to coat the surface of polymeric materials to meetaesthetic requirements or to provide a protective surface to help thepolymeric substrate withstand degradation. Providing a high qualitydurable painted surface on certain polymeric substrates has beenproblematic due to generally poor surface adhesion qualities exhibitedby various polymeric substrate materials. Poor surface adhesion is alsoproblematic in situations in which other laminates, films or metalliclayers are to be imparted onto the polymer. Situations can also includebonding of one polymer substrate to another polymeric material or tonon-polymeric substrates.

To this end, much activity has been devoted to providing polymers withimproved surface adhesion characteristics and to improving the surfaceadhesion characteristics of known polymeric materials. Methods includeroughening of polymeric surfaces by exposure to strong mineral acidswith or without the presence of strong oxidizers such as chromates,permanganates and the like.

Other adhesion promotion methods involve the use of strong mineral acidsin combination with concentrated mineral oxidants and strong mineralacid salts in aqueous treatment solutions. This art is taught in U.S.Pat. No. 3,869,303 to Orlov et al. Problems associated with the use ofsuch strong mineral acids and toxic oxidizers include handling anddisposal risks as well as the potential that the polymeric surface andsubstrates may be excessively degraded or compromised. Additionally, itis possible that the resulting polymeric substrate surface may besusceptible to unwanted oxidation or the like, necessitating immediatecoating with the desired coating material.

Treatment of polyolefin materials for adhesive bonding using anon-chromate solution containing sulfuric acid in the presence of eitherlead dioxide, potassium iodate or ammonium persulfate is taught in U.S.Pat. No. 4,835,016 to Rosty et al. The Rosty reference also discussesthe use of a solution containing bleach and detergent. In order to beeffective, the Rosty reference teaches that the polymeric samples mustbe submersed in the prescribed solution for several days. Suchprotracted exposure is simply not practical in many treatmentoperations.

Treatment methods are also known which teach the use of peroxydisulfuricacid solutions with the optional use of accelerants capable ofactivating peroxydisulfuric acid oxidation reactions. In U.S. Pat. No.3,695,915 to Morris, metal salts such as copper, ferrous or silver saltsof sulfuric acid or nitric acid are employed to increase the rate ofevolution of oxygen. Care must be taken in employing the processdisclosed in Morris lest excess concentrations of deleterious sulfuricacid are produced.

In U.S. Pat. No. 5,05,256 to Haag, a method for improving adhesion ofpaints to polydicyclopentadiene is proposed. A solution containingsodium hypochlorite and, preferably, a detergent is applied to thepolymer by wiping. The solution is allowed to remain on the polymersurface for a 40 minute interval and is then washed off.Polydicyclopentadiene presents a unique and exotic polymeric structure.Without being bound to any theory, it is believed that the large numberof unsaturated carbon--carbon linkages in the cyclic functionalitiesprovides a material uniquely susceptible to interaction withhypochlorite compounds. Unfortunately, the method described in Haag hasnot been readily adaptable to other more commonplace polymers.

Heretofore, no method has been proposed which promotes surface adhesioncharacteristics of a broad range of polymeric substrates in anefficient, economical manner which reduces reliance on chemicalcompounds which present handling and disposal difficulties; and, it isan object of the present invention to provide such a method. Since manyof the compounds previously suggested for polymeric adhesion promotionare costly, difficult to obtain, or present handling or disposalproblems, it is a further object of the present invention to provide amethod for improving surface adhesion characteristics of commonpolymeric substrates which employs relatively low-cost chemicalcommodities in an easily handled fluid medium such as an aqueoussolution which does not require undue special handling considerations.It is a further object of the present invention to provide a method andcomposition which may be incorporated into the polymeric material at anypoint in its processing, using either an aqueous solution or ananhydrous mixture of reagents, thereby advantageously rendering apolymeric material which is paintable and/or exhibits improvedadherability characteristics. It is also desirable that the method yieldrelatively consistent treatment results and be easy to implement andmonitor in a plant or manufacturing setting. It is desirable thatimprovements in polymeric surface adhesion be accomplished in a rapidand uniform manner over the entire targeted polymeric surface area.Finally, it is desirable that the adhesion improvement method be onewhich yields sufficiently permanent improvement in adhesioncharacteristics without unduly compromising other performancecharacteristics of the polymer.

SUMMARY OF THE INVENTION

The present invention is a method for improving surface adhesioncharacteristics of a polymeric substrate or virgin polymeric material inwhich the portion of the surface of the polymeric substrate and/orentire virgin polymeric material to be treated is contacted with acomposition containing at least one oxidizing agent. The oxidizing agentin the composition employed in the method of the present invention ispresent in a kinetically degrading state capable of producing at leastone chemical intermediate which is reactive with the polymericsubstrate/virgin polymeric material. Contact between the compositioncontaining the oxidizing agent and the polymeric substrate/virginpolymeric material is maintained for an interval sufficient to modifyfunctional groups present in the polymeric substrate/virgin polymericmaterial. The oxidizing agent of choice is a halogenated bivalent oxygencompound. In the process of the present invention, the halogenatedbivalent oxygen compound of choice is one which is capable of acontrolled rate of oxidation and capable of activation to yield thedesired kinetically degrading state. Activation may occur by anysuitable mechanical or chemical mechanism by an activator agentcontaining a compound having at least one carboxylic acid group, acarboxylic acid derivative, or synthetic equivalents thereof. Theactivator agent may be present in the composition upon initial contactwith the polymeric substrate/virgin polymeric material or may be addedto the composition subsequent to initial contact with the polymericsubstrate/virgin polymeric material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is predicated upon the unexpected discovery that adhesioncharacteristics of a polymer substrate, particularly adhesioncharacteristics between the polymer substrate and an applied organicfilm can be significantly enhanced by processing the polymeric substratewith a solid, fluid and/or vaporous material which contains at least oneoxidizing agent. It is to be understood that the processing/treatmentaccording to the present invention may take place at any point inmanufacture of the substrate, from treatment of the virgin polymericmaterial, and/or treatment of the material during molding/forming into asubstrate, and/or treatment of the substrate after forming.

The oxidizing agent of choice is a bivalent oxygen compound present inthe fluid material in a kinetically degrading state. The oxidizing agentis capable of producing at least one chemical intermediate which issignificantly reactive with functionalities present in the polymericsubstrate. The kinetic degradation of the oxidizing agent is enhanced oraugmented by the presence of an activator agent. The activator agent ofchoice is one containing a chemical compound which has at least onecarboxylic acid group, a carboxylic acid derivative, or syntheticequivalents thereof. It has been found, quite unexpectedly, thatoxidation of the bivalent oxygen compound proceeded at a controlled ratewhich is made useful by the creation of the kinetically degrading state.

As used herein, the term "kinetically degrading state" is defined as anon-equilibrium state in which the oxidizing agent, specifically thehalogenated bivalent oxygen compound experiences a change in oxidationstate over time with the oxidizing agent having its highest oxidationnumber in its highest concentration at a point closest to the initiationof the reaction process with a concomitant decrease in concentration ofthis species over time. The concentration of oxidizing agents havinglower or lowest oxidation states is at its lowest at the outset of themethod of the present invention with a concomitant increase in thisspecies over time. The kinetically degrading state of the oxidizingagent produces at least one chemical intermediate which is reactive withthe polymeric substrate. The chemical intermediate may be stable,unstable or transient. Stable intermediates can be defined herein asthose which are readily isolatible for quantification and analysis.Unstable intermediates are defined herein as those which cannot beisolated for such quantification and analysis. Transient intermediatesare considered those which react rapidly with the polymeric substrate orother components present in the system. Theoretic concepts for thechemical intermediates are presented subsequently.

As used herein, the term "oxidizing agent" is a chemical compound whichreadily gives up oxygen, accomplishes the removal of hydrogen fromanother, preferably organic, compound or serves to attract negativeelectrons to accomplish the eventual hydrogen removal from the targetcompound.

The term "controlled rate of oxidation" as used herein is defined as achemical reaction rate which proceeds with efficient evolution ofquantities of reactive intermediate sufficient to interact with thepolymeric substrate. The oxidation process proceeds without generationof excessive quantities of by-product such as devolved gaseous productor the like.

In the method of the present invention, polymeric substrates or virginpolymeric materials for which adhesion improvement can be effected are,generally, those having hydrogens attached to carbon atoms characterizedby large percentages of covalent carbon bonds; typically alkane linkagespresent throughout the polymeric lattice. Without being bound to anytheory, it is believed that the presence of large numbers of covalentbonds in the polymeric lattice renders the polymeric material relativelyunreactive and difficult to make adhesive. The polymeric materials ofchoice may be either thermosetting or thermoplastic materials. Examplesof suitable polymers include addition polymers selected from the groupconsisting of polyolefins, substituted polyolefins, and polyolefinblends. Preferred polyolefins are addition polymers selected from thegroup consisting of polyethylene, polypropylene polyisobutylene,polystyrene, polyisoprene, polyethylene terephthalate, polybutyleneterephthalate, polyvinyl chlorides, polyvinylidine chlorides,polyacrylonitriles, polyvinylacetates, and mixtures thereof. It has beenfound that the process of the present invention is particularlyefficacious when performed on these addition polymers. Adhesiveproperties inherent in certain polyolefin addition polymers areparticularly low. Modification of such properties to increasepaintability of the polyolefin is highly desirable and, heretofore,limitedly successful.

While the process of the present invention is particularly directed topolyolefin addition polymers, it is to be understood that the processcan also be employed to increase adhesive properties of other polymerswhich are generally recognized as more paintable. These latter polymersinclude halogenated polyalkyls and polyalkyl acrylates, selected fromthe group consisting of polyvinyl chloride, polymethyl methacrylate,polymethyl acrylate, and mixtures thereof.

Polyethylenes composed of substituted or unsubstituted alkalene monomersmay also be treated by the process of the present invention. Examples ofsubstituted alkylene polymers include polytetrafluoroethylene,polytrichlorofluoroethylene and the like. Finally, other additionpolymers can successfully be treated. This includes materials such aspolyformaldehyde, polyacetaldehyde, polyisoprene and the like.

Condensation polymers which exhibit marked increases in adhesive abilityinclude polyesters selected from the group consisting of polyethyleneterephthalate, polybutylene terephthalate, and mixtures thereof. Otherpolymeric materials which can be treated by the process of the presentinvention can be condensation polymers such as those selected from thegroup consisting of polyamides, polyesters, polyurethanes,polysiloxanes, polyphenolformaldehydes, urea formaldehydes,melamineformaldehydes, cellulose, polysulfides, polyacetates,polycarbonates, and mixtures thereof.

The polymeric material employed in the substrate or virgin polymericmaterial can also be a thermoplastic elastomer selected from the groupconsisting of styrene-isoprene-styrene, styrene-butadiene-styrene,copolyesters, copolyester ethers, silicone-polyamides,silicone-polyesters, silicone-polyolefins, silicone-styrenes, aromaticpolyether-urethanes, alpha cellulose filled ureas, polyvinylchloride-acetates, vinylbutyrals, and mixtures thereof.

The polymeric material employed in the substrate or virgin polymericmaterial may further be a co-polymer selected from the group consistingof polyester-polyethers, polyether-polysiloxanes,polysiloxane-polyamides, polyesteramides, copolyamides, nylons, andmixtures thereof.

Various other polymeric materials suitable for use as the substrate orvirgin polymeric material include those listed in Modern Plastics,"Appendix: Numerical Specification Index," Mid-November 1995, atB-143-B-144.

It is also within the purview of this invention that the polymericsubstrate or virgin polymeric material can be a blend containing as amajor constituent any of the enumerated polymers.

It is to be understood that various polymeric substrates or virginpolymeric material have varying degrees of adhesion ability. Thus, themethod of the present invention is most efficaciously employed forimproving polymeric materials with relatively poor initial adhesioncharacteristics such as polyolefin polymeric substrates/virgin polymericmaterials, polyester polymeric substrates/virgin polymeric materials,and mixtures thereof. The specific polymeric substrates/virgin polymericmaterials for which the adhesion improvement method of the presentinvention shows the most dramatic results are polymers selected from thegroup consisting of polyethylene, polypropylene, polystyrene,polyisobutylene, polyethylene terephthalate, polybutylene terephthalateand mixtures thereof. It is anticipated that the polymeric substratesmost advantageously improved by the process of the present invention arethose which contain one or more of the enumerated polymers as a majorconstituent thereof. It is also within the purview of this inventionthat the polymeric substrate may include other compounds such asplasticizers, fillers, oxidation stabilizers, colorants, and the likecompatible with the adhesion improvement method of the presentinvention.

In the method of the present invention, at least a portion of thesurface area of the polymeric substrate is contacted with a fluidmaterial containing at least one oxidizing agent. It is anticipated thatthe method of the present invention can be successfully implemented onpolymeric material which has been formed, extruded, or otherwiseprocessed into a finished or intermediate part generally consideredready for painting or other processing for which increased adhesioncharacteristics are desired. Examples of such processes include, but arenot limited to, joining, laminating and the like. It is within thepurview of this invention that the entire polymeric substrate becontacted with the fluid material containing the oxidizing agent.However, it is also within the purview of this invention that thepolymeric substrate be masked or otherwise prepared so that only thedesired portion of the surface area of the polymeric substrate be sotreated.

The fluid material containing the oxidizing agent may be any liquid orgaseous composition which is capable of containing and conveying theoxidizing agent into contact with the polymeric substrate surface to betreated. Preferably, the fluid material is an aqueous solutioncontaining sufficient quantities of the oxidizing agent to effect theappropriate chemical reaction in the desired manner at the desired rate.

The oxidizing agent of choice is one which is capable of kineticallydegrading from its highest oxidized state into lower intermediates in acontrolled or controllable reaction mechanism. The oxidizing agent mayalso be a material which can be rendered capable of such kineticdegradation in a controlled rate of reaction.

The oxidizing material employed in the method of the present inventionis a compound which will generally evolve halogen or a halogen analog ata controlled rate, particularly when brought into contact with materialscontaining functionality of carboxylic acid, carboxylic acid derivative,or synthetic equivalents thereof. As used herein, the term "halogen or ahalogen analog" is defined as one of the electronegative elements ofGroup VIIA of the Periodic table or a material which will perform thesame or similar function in the process of the present invention.Halogens preferably are selected from the group consisting of chlorine,bromine, iodine and mixtures thereof. Halogen analogs preferably areselected from the group consisting of boron, nitrogen and mixturesthereof.

In the process of the present invention, the oxidizing agent of choiceis a halogenated bivalent oxygen compound which is selected from thegroup consisting of oxycompounds of chlorine, oxycompounds of bromine,oxycompounds of nitrogen, and mixtures thereof. Without being bound toany theory, it is believed that the selected oxidizing compoundskinetically degrade into an intermediate.

Oxycompounds of chlorine which can be utilized as the bivalent oxygenoxidizing agent are selected from the group consisting of hypochlorousacid, alkali metal salts of hypochlorous acid and hydrates thereof,alkaline earth metal salts of hypochlorous acid and hydrates thereof,perchloric acid, alkali metal salts of perchloric acid and hydratesthereof, alkaline earth metal salts of perchloric acid and hydratesthereof, chloric acid, alkali metal salts of chloric acid and hydratesthereof, alkaline earth metal salts of chloric acid and hydratesthereof.

Oxycompounds of bromine which can be utilized as the bivalent oxygenoxidizing agent are selected from the group consisting of hypobromousacid, alkali earth metal salts of hypobromous acid and hydrates thereof,alkaline earth metal salts of hypobromous acid and hydrates thereof,bromic acid, alkali metal salts of bromic acid and hydrates thereof,alkaline earth metal salts of bromic acid and hydrates thereof.

Oxycompounds of iodine which can be employed as the bivalent oxygencompound of the present invention are selected from the group consistingof iodic acid, alkali metal salts of iodic acid and hydrates thereof,alkaline earth metal salts of iodic acid and hydrates thereof, periodicacid, alkali metal salts of periodic acid and hydrates thereof, alkalineearth metal salts of periodic acid and hydrates thereof.

Oxycompounds of boron which can be employed as the bivalent oxygencompound of the present invention are selected from the group consistingof boric acid, alkali metal salts of boric acid and hydrates thereof,alkaline earth metal salts of boric acid and hydrates thereof, perboricacid, alkali metal perborates and hydrates thereof, alkaline earth metalperborates and hydrates thereof.

Oxycompounds of nitrogen which can be employed as the bivalent oxygenoxidizing agent are selected from the group consisting of nitric acid,alkali metal salts of nitric acid and hydrates thereof, alkaline earthmetal salts of nitric acid and hydrates thereof.

The oxycompound of choice is preferably a compound or mixture ofcompounds which will kinetically degrade in a controlled, essentiallysteady manner to provide chemical intermediates which are reactive withthe polymeric substrate.

Preferred oxycompounds employed as the oxidizing agent in the process ofthe present invention are selected from the group consisting ofhypochlorous acid, alkali metal salts of hypochlorous acid, hydrates ofhypochlorous acid, alkaline earth metal salts of hypochlorous acid,hydrates of alkaline earth metal salts, and mixtures thereof. Examplesof oxidizing agents include hypochlorous acid, calcium hypochlorite,sodium hypochlorite, calcium hypochlorite tetrahydrate, lithiumperchlorate, lithium perchlorate trihydrate, magnesium perchlorate,magnesium perchlorate dihydrate, potassium chlorate, sodium perchlorate,lithium nitrate, magnesium iodate tetrahydrate, magnesium nitratehexahydrate, nitrosalicylic acid, sodium perborate tetrahydrate. In thepreferred embodiment, the oxidizing agent is selected from the groupconsisting of hypochlorous acid, calcium hypochlorite, sodiumhypochlorite, lithium perchlorate, magnesium perchlorate, sodiumperchlorate, potassium chlorate, and mixtures thereof. In the mostpreferred embodiment, the oxidizing agent is selected from the groupconsisting of sodium hypochlorite, calcium hypochlorite, calciumhypochlorite tetrahydrate, and mixtures thereof.

The oxidizing agent is preferably present in aqueous solution in aconcentration sufficient to provide material which can kineticallydegrade to an intermediate which will interact with the polymericsubstrate with which it is brought into contact.

In the process of the present invention, the oxidizing agent ismaintained in an aqueous solution at a concentration between about 0.25%and 25% by volume, with an oxidizing agent concentration between about0.5% and about 5.25% by volume being preferred and an oxidizing agentconcentration between about 2.6% and about 5.25% by volume being mostpreferred. It should be noted that an oxidizer concentration of 5.25% isthe concentration of bleach. It is also to be understood that theoxidizing agent of the present invention may be used in solid form,and/or as a solid(s) suspension.

It is within the purview of the present invention that other liquid orgaseous material can be employed as an activating agent for theoxidizing agent, provided that the liquid or gaseous material does notadversely interact with the oxidizing agent or polymeric substrate.Aqueous solutions may be preferred for purposes of economy and handlingease. However, it is also to be understood that the activating agent ofthe present invention may be used in solid form, and/or as a solid(s)suspension.

The oxidizing agent may be employed in combination with a suitableactivating agent capable of preferably reacting with the oxidizing agentto produce the intermediate species which is, in turn, reactive with thepolymeric substrate. The activating agent is an organic material orderivative thereof having at least one carboxylic acid functionality orderivative thereof.

The activating agent employed in the process of the present invention isselected from the group consisting of carboxylic acids, anhydridederivatives of carboxylic acids, and halide derivatives of carboxylicacids, selenic acid derivatives of carboxylic acids, perchloric acidderivatives of carboxylic acid, boric acid derivatives of carboxylicacid dicarboxylic acid, anhydride derivatives of dicarboxylic acid, acidhalide derivatives of dicarboxylic acid, selenic acid derivatives ofdicarboxylic acid, boric acid derivatives of dicarboxylic acid,synthetic equivalents of the above-mentioned compounds, and mixturesthereof.

Carboxylic acids suitable for use as an activating agent have thegeneral formula shown immediately below. Note that the "HI" or the "OH"in the following formula may or may not be present in some of thederivatives, eg. acid chlorides and DCC coupled carboxylic acids (usedin peptide chemistry). Some of these derivatives, such as the acidchlorides, may be too reactive to exist in aqueous solutions and quicklybreak down to the corresponding carboxylic acid. It is possible that theacid chlorides could be added to the present reaction mixture with theexpectation that they would break down to form the desired activatingcompound. Some other additional suitable "acids" may includehydroxylamine hydrochloride, phosphorous pentachloride, phosphorouspentoxide, phosphoryl chloride, sulfurous acid, sulfuryl chloride,thionyl chloride, and, less preferably, phenols and catechols (these areboth weakly acidic). The carboxylic acid general formula is as follows:##STR1## wherein x and y are integers between 0 and 20 inclusive withthe sum of x and y being an integer of 20 or less, wherein R is afunctionality selected from the group consisting of substituted orunsubstituted aromatic hydrocarbon groups, branched or unbranched alkylgroups, the alkyl group having between 1 and 27 carbon atoms, andmixtures thereof, and wherein each variable R', R", R'" and R"" is afunctionality selected from the group consisting of hydrogen, amines,hydroxyl, phenyl, phenol radicals, and mixtures thereof, each of theabove-mentioned R variable functionalities being chosen independently ofthe other R variable functionalities, and wherein R" may also beselected from the group consisting of anhydrides, halide salts, selenicacid salts, perchloric acid salts, boric acid salts, and mixturesthereof.

Dicarboxylic acids suitable for use as an activating agent have thegeneral formula: ##STR2## wherein x is an integer between 1 and 20inclusive, and R and R' are functionalities selected from the groupconsisting of hydrogen, hydroxyl radicals, amines, phenol radicals, andmixtures thereof.

It is to be understood that the numbers mentioned above in both formulaefor the number of carbons represented by "x" and "y" represent most"simple" molecules. However, it is to be understood that these formulasare illustrative, and the present invention is not to be limitedthereto. Within the purview of the present invention, there is no reallimit on the number of carbons represented by "x" and "y." In theextreme case of polymers, x and y would simply be between 2000 and500,000. Also, in the instance of polymers, the number and distributionof x and y could vary greatly from ordered to random and fromalternating to block.

Although it is to be understood that suitable polymers are contemplatedas being effective activating agents, testing seems to indicate that anyincrease in chain length tends to compete with the polymer being treatedfor the reactive species. This was true for both the addition ofsurfactants and PEG as well as PVA. In the case of the surfactant, therate of treatment was greatly decreased. In the case of both PEG andPVA, attempts to mix them with sodium hypochlorite resulted in a violentreaction. This would suggest that these polymers could thus diminish theperformance of the system by reacting with the reactive species insolution as opposed to the polymer to be treated. It is to beunderstood, however, that this may not always be the case.

An example of a polymer which may degrade in water to yield an acidsuitable for use as the activating agent includes, but is not limited topolyphosphoric acid. Examples of suitable acidic polymers include, butare not limited to poly(melamine-co-formaldehyde)s, polyacrylic acids,and salts thereof.

Further, regarding each of the R variables mentioned hereinabove, ie. R,R', R", etc., it is to be understood that the R groups are not intendedto be limited to the above-identified species. For example, in a randombranched polymer, the R groups may include a nearly infinite array; eg.the R groups may contain repeating ether linkages (such as in PEG),repeating amide linkages (such as in the polyamides), etc. The R groupsmay also contain combinations of any variety of functional groups.Another possibility is that one R group may be attached to another Rgroup forming a ring. These rings may also contain functionality andbranching. Furthermore, any of the branches in any of the aforementionedsystems may be terminated with an additional functional group. A partiallisting of functional groups that are commonly found in or at the end ofmolecules include: ethers, esters, amides, ketones, aldehydes, alcohols,nitrites, alkenes, alkynes, cyano groups, sulfur, sulfates, phosphor,phosphates, nitrogen, amines, nitro groups, as well as diazonium speciesetc. This presents a nearly infinite array of possibilities.

Suitable carboxylic acids include butyric acid, lactic acid, propionicacid, heptanoic acid, formic acid, and mixtures thereof. Derivatives ofthese mild carboxylic acids are also contemplated, as well as syntheticequivalents thereof. Specifically contemplated are acid anhydrides, acidchlorides, acid bromides and polyacids, such as heptanoic acid, butyricanhydride, heptanoic anhydride and the like. Examples of acid chlorideswhich can be effectively employed include palmitic chloride, fumerylchloride, and the like.

Suitable dicarboxylic acids, acid derivatives, and synthetic equivalentsthereof include dicarboxylic acids such as oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid,and fumaric acid. It is within the purview of this invention that theactivating agent be a mixture of these compounds. It is also within thepurview of this invention that the activating agent be a derivative ofdicarboxylic acid including, but not limited to, acid anhydrides, acidchlorides, acid bromides and polyacids. Particular examples of theseinclude, but are not limited to materials such as acetic anhydride,oxalic acid dihydrate, acetile bromide, acetile chloride, 2 acetilebenzoic acid, 4 acetile benzoic acid, bromoacetic acid, acetic acid,glacial acetic acid, vinegar, calcium oxylate, chlorobenzoyl chloride, 3chlorobenzoyl chloride, citric acid, citric acid monohydrate,bibenzilazodicarboxylate, diglycolic acid, fumaric acid, furmerylchloride, galic acid, galic acid monohydrate, oxalic acid, subasic acid,pyruvic acid, succinic acid, succinic anhydride, succinyl chloride, 5sulfosalicylic acid, tannic acid, tartaric acid, and mixtures thereof.

An additional class of dicarboxylic acids includes the bridgedcarboxylic acids of the phthalate and succinimide types, such asterephthalic acid and succinimide.

It is to be understood that the amino acids and poly-amino acids formanother class of acids contemplated as being effective activatingagents. Suitable examples thereof include, but are not limited toaspartic acid and polyaspartic acid.

In the preferred embodiment, the activating agent of choice is onewhich, when added to the solution containing the oxidizing agent willresult in the dissolution of the activating agent and dispersalthroughout the solution. The addition of activating agent may also leadto an increase in solution temperature depending upon the particularactivating agent employed and the amount added. Preferably, the amountand particular activating agent employed produces a rate of kineticdegradation of oxidizing agent which is manageable and yields atreatment solution which will provide for prolonged successful polymericsurface adhesion promotion. Ideally, the rate of kinetic degradation isone which will permit use of the treatment solution for intervalsupwards of a day before replacement or recharging is required, with useintervals of seven to ten days being preferred. The interval duringwhich the treatment solution is active will vary depending uponparameters such as temperature, the amount of polymeric substratetreated and the like.

In the process of the present invention, the activating agent ismaintained in an aqueous solution at a concentration between about 0.01%and 5.0% by volume, with an activating agent concentration between about0.05% and about 0.53% by volume being preferred, and an activating agentconcentration between about 0.26% and about 0.53% by volume being mostpreferred.

In the process of the present invention, the activating agent materialis preferably one which will promote dissolution of the activatingmaterial without liberation of undesirable gasses such as halogen gas orother unsuitable byproducts. In the preferred embodiment, the amount ofactivating agent employed is that sufficient to produce reactiveintermediate capable of adhering to and/or interacting with thepolymeric substrate. In the preferred embodiment, it is anticipated thatthe reactive intermediates react with the plastic substrate to addfunctionality which improves the adhesive properties of the polymericmaterial without unduly compromising polymeric performance.

Other compounds, although less preferred, may be used as the activatingagent, including but not limited to potassium acetate, hydrochloricacid, and hydrogen peroxide.

It is to be understood that radical initiators are also contemplated asbeing effective activating agents. Some suitable examples include, butare not limited to 2,2-Azobis(2-methylpropionitrile) (AIBN), benzoylperoxide, 4-bromomethyl-2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxylfree radical, and 3-chloroperoxybenzoic acid. It is to be furtherunderstood that the activating agent may include a mixture of: any ofthe suitable acid activating agents disclosed herein; and any of thesuitable radical activating agents disclosed herein.

It is to be yet further understood that the solid supported acids oracid catalysts are also contemplated as being effective activatingagents. These include three main categories: ion exchange resins; otherresins to which acidic functionality has been added; and acid washedresins. Resins that could be used, modified and/or acid washed includepaper, cellulose, starch, magnesium silicate, calcium silicate, silica,silicon dioxide, silicic acid, fluoricil, magnesium oxide, alumina, andactivated carbon.

In the most preferred embodiment, the activating agent is selected fromthe group consisting of acetic anhydride, oxalic acid, formic acid,glacial acetic acid, acetic acid, vinegar, and mixtures thereof. Anadvantage of both glacial acetic acid and vinegar is that they are eachless noxious than acetic anhydride and pose much less of a potentialinhalation hazard than is possible with acetic anhydride. Although theuse of acetic acid or vinegar as the activating agent may render apolyolefin material somewhat less paintable than would use of an aceticanhydride activating agent, its (their) use may be desirable for theabove reasons.

Although less preferred than acetic anhydride, acetic acid or vinegar,an advantage of oxalic acid is that it is a solid at room temperatureand is thus relatively easy to handle and clean up. Oxalic acid also hasno significant odor and thus may eliminate a potential inhalation hazardwhich may be associated with the use of acetic anhydride (a stronglacrimator).

Without being bound to any theory, it is believed that the reactionproceeds according to the following mechanism. In that reactionmechanism, admixture of a hypochloride material such as sodiumhypochloride in water yields the predominant active species hypochlorousacid as outlined in Equation I. ##STR3## Without being bound to anytheory, it is believed that the activating agent may react with theoxidizer as exemplified by the reaction of oxalic acid with hypochlorousacid. It is believed that oxalic acid activates the hypochlorous acidand functions as a lewis acid to yield a hydroxyl ion. A radicalreaction between hypochlorous acid and oxalic acid may thus proceedyielding hydrochloric acid, carbon dioxide and a carboxyl radical withconcomitant generation of carbon dioxide as hypothesized in Equation II.##STR4## The radicals formed in the initial decomposition may reactdirectly with the polymeric substrate, react to form other radicals, orcombine in termination steps to remove the reactive species fromsolution. One example of a radical reaction to form other radicals isoutlined in Equation III. ##STR5## Examples of theoretical terminationreactions are outlined in Equations IVa and IVb. ##STR6## Representativeexamples of reactive species reacting with functional groups on thepolymeric substrate, in this instance, polyethylene, are set forth inEquation V. ##STR7## Similar theoretic mechanisms for activation ofhypochlorous acid can be presented using acetic anhydride as outlined inEquation VI. ##STR8## In such cases, further decomposition of the formedspecies would likely occur in manners such as that outlined in EquationVII. ##STR9##

An alternate theoretic mechanism for decomposition of acetic anhydrideis set forth in equation VIII. Acetic anhydride acts as a lewis acidattracting hypochloride ion present in solution to produce an activatedoxidizer and a carboxylate salt. See Equation VIII below. ##STR10## Theactivated oxidizer interacts with the polymeric matrix to yield apolymeric substrate reactive to either carboxylate radicals as outlinedin Equation IXa or chlorine radicals as outlined in Equation IXb.##STR11##

It is to be understood that the reaction mechanisms discussed arehypothetical. Without being bound to any theory, it is surmised that theforegoing provides depiction of possible reaction mechanisms occurringin the process of the present invention.

Thus, it is theorized that the process of the present invention resultsin the addition of discrete functionality at locations in the polymericmatrix previously occupied by a hydrogen atom. Because this reaction islimited to the polymeric matrix at or near the exterior surface of thearticle to be treated, localized addition of functionality does notunduly compromise performance characteristics of the polymer as mayoccur with integration of functionality throughout the substrate.

This is particularly important when treating polymeric materials inwhich there are few or no functional groups initially, such as is thecase with polyethylene and polypropylene. By the process of the presentinvention, desired functional groups can be inserted into the matrix ina randomized fashion at locations proximate to the exterior surface. Theadded functionality provides greater chemical and mechanochemicalinteraction with the material to be adhered, eg. paint.

The following Table and test data illustrate various formulations andexperimental results according to the present invention, and illustratethe longevity of the various formulation baths before the baths had tobe replaced and/or regenerated. It is to be understood that thefollowing Table and test data contain formulations provided forillustrative purposes and are not to be construed as limiting the scopeof the present invention.

Paint adhesion was examined using test method ASTM D3359-78, wherein thepainted surface was cross-hatched; a piece of transparent tape wassecured to the surface; and the tape was then peeled off at about a 90°angle. Paint adhesion was also examined by a variation of test methodASTM D3359-78 wherein the painted surface was not cross-hatched. In thefollowing experiments, the bath was considered operative untilsubsequent painting (with 2 coats of RUST-OLEUM Gloss Protective SprayEnamel, Gloss Black 7779) and testing of sample pieces revealed a dropof adhesiveness to paint of approximately 50% from a startingadhesiveness of >98% as measured qualitatively by visual inspection. Thedrop was generally sudden.

For the experiments characterizing bath life described below, thetreatment time was 24 hours. All these experiments were executed at roomtemperature (RT).

    ______________________________________                                        EXPERIMENT                                                                              FORMULATION      BATH LIFE (DAYS)                                   ______________________________________                                        I         50     mLs bleach    1                                                        1      mL Ac.sub.2 O.sup.1                                          II        50     mLs bleach    1                                                        1      mL Ac.sub.2 O                                                III       50     mLs bleach    2                                                        50     mLs phosphate buffer                                                   6      mLs Ac.sub.2 O                                               IV        50     mLs bleach    7                                                        50     mLs H.sub.2 O                                                          1      mL Ac.sub.2 O                                                V         50     mLs bleach    5                                                        50     mLs phosphate buffer                                                   1      mL Ac.sub.2 O                                                VI*       5      mLs bleach    5                                                        50     mLs H.sub.2 O                                                          1      mL Ac.sub.2 O                                                VII*      25     mLs bleach    5                                                        50     mLs H.sub.2 O                                                          1      mL Ac.sub.2 O                                                ______________________________________                                         .sup.1 Acetic anhydride                                                       *The VI and VII results were slightly worse than those of IV and V.      

Miscellaneous experimentation revealed the following data: 1. It wasfound that 50% H₂ O₂ did not yield adhesion after six days at roomtemperature; 2 Polymer dispersions and NaOH decrease effectiveness oftreatment; 3. Elmer's Contact Cement and Testor's Plastic Cement exhibitpoor adhesion to treated PE and PP. Dow Silicone Adhesive exhibitedexcellent adhesion to PE and PP pieces; 4. Ca(OCl)₂ could be used inplace of NaOCl to prepare adhesive surfaces; 5. It was found that Cl₂gas and Cl₂ in solution prepared by adding HCl to bleach providedadhesive surfaces on PE; and 6. The effects of added glycerol and KOAcwere also examined and provided decreased performance.

Although the exposure method described in the present invention is thatof dipping the polymer into a bath containing the treatment solution, itis to be understood that the polymer may be exposed to the treatmentsolution by any suitable method, including but not limited to spraying aheated treatment mist onto the polymer, spraying a treatment mist onto aheated polymer, and the like.

Some alternate methods of the present invention for treating thepolymer(s) are discussed hereinbelow. The polymeric articles may betreated at other times during their processing. For example, a solutionas disclosed hereinabove, or an anhydrous mixture of reagents disclosedhereinabove could be fed directly into the mouth of a press screw via ahopper or other means. The polymer beads used in processing could alsobe treated at the polymer manufacturer prior to shipment to the OEM orother manufacturer. As the beads are melted in the barrel or screw, thetreated surfaces would be mixed throughout the polymer melt. Aftershooting the part, some of the treated material would be exposed, thusrendering a polymeric article paintable and/or adherable after moldingwithout need for post-molding treatment before application of paint orthe like.

It is believed that these concepts are novel in that they may not onlyfind utility in promoting adhesion, but may impart unexpected and novelproperties on the polymer through polymer crosslinking, or by increasingpolymer compatibility. A new type of ultra-high molecular weightbranched polyethylene (PE) or other plastic may result, therebyproviding for increased stiffness and impact strength. A PE capable ofbeing blended with less expensive non-block elastomers or other polymersmay also result. Further, the necessity of compatibilizer use may bereduced.

For example, a polyolefin material may be prepared by submersing it in asuitable solution of the inventive oxidizing agent and activating agent,under suitable conditions, until the polyolefin is wetted. The materialmay then be further processed, thereby treating the polyolefin materialaccording to the present invention. The treated polyolefin material maythen be mixed with previously incompatible polymers, thereby producingnovel copolymer blends upon processing.

The treated polyolefin material may alternately be mixed with a reactivepolymer, thereby forming novel, highly crosslinked, strong structuralpolymers upon processing. Crosslinking of, for example, polyethylene,increases its strength properties and extends the upper temperaturelimit at which this plastic can be used.

The treated polyolefin material may alternately be mixed with severalunlike polymers, thereby making them compatible.

Further, the treated polyolefin material may alternately be mixed with areactive polymer and shipped prior to processing or after partialreaction. The novel polymer blend may then be used as a novel, highlycrosslinked thermoset polymer.

The present invention provides a novel, greatly improved chemical methodfor enhancing the adhesive properties of polymer surfaces, for example,the surfaces of olefinic polymers such as polyethylene andpolypropylene. The inventive method includes, but is not limited to thefollowing advantages: it is relatively non-toxic, highly effective, andvery fast.

Possible applications for the present inventive method may include, butare not limited to an expanded use of polymers, such as, for example,olefinic polymers such as polyethylene and/or polypropylene, for:paintable auto parts; house and garden products; medical devices coatedwith biocompatible materials; new manufacturing techniques involvinggluing polyethylene and/or polypropylene pieces together (a replacementfor heat welding and mechanical joints); use of polyethylene and/orpolypropylene films as laminates to prepare chemical resistant surfaces;and for providing containers and structural components with increasedphysical properties.

To further illustrate the composition, the following examples are given.It is to be understood that these examples are provided for illustrativepurposes and are not to be construed as limiting the scope of thepresent invention.

EXAMPLE 1

Approximately 1.25 inch by 1.25 inch squares of high densitypolyethylene (HDPE) were chosen as samples. The HDPE samples wereprocessed by structural foam injection molding, and could contain up to4% white pigment and blowing agent, and up to 10% calcium carbonate. Thesamples were immersed in a standard bleach solution commerciallyavailable from the Clorox Company under the trademark CLOROX (5.25%sodium hypochlorite) for 48 hours at room temperature. The thus treatedsamples were painted with KRYLON ColorWorks Spray CWA1150 Gloss Black,Quick Dry Lacquer. Paint adhesion was examined by test method ASTMD3359-78 wherein the painted surface was cross-hatched; a piece oftransparent tape was secured to the surface; and the tape was thenpeeled off at about a 90° angle. Paint adhesion was also examined by avariation of test method ASTM D3359-78 wherein the painted surface wasnot cross-hatched. Under either test method, adequate paint adhesion wasnoted upon visual inspection.

EXAMPLE 2

Calcium hypochlorite solutions were prepared by dissolving a commercialbrand of 67% calcium hypochlorite in water to make a saturated solution.Several approximately 1.25 inch by 1.25 inch squares of high densitypolyethylene (HDPE) (formed by injection molding as described inExample 1) samples were immersed in the solution for 48 hours at roomtemperature. The samples were then painted with KRYLON ColorWorks SprayCWA1150 Gloss Black, Quick Dry Lacquer. Paint adhesion (as determinedusing the test methods described in Example 1) to a slightly greaterextent than that obtained in Example 1 was noted upon visual inspection.

EXAMPLE 3

Several polypropylene samples were boiled in the bleach solution ofExample 1 for about one hour. The samples were then painted with KRYLONColorWorks Spray CWA1150 Gloss Black, Quick Dry Lacquer. Excellent paintadhesion was noted upon visual inspection, as determined using the testmethods described in Example 1.

EXAMPLE 4

Untreated polyethylene pieces were glued together using "Super Glue."The pieces were pulled apart easily. Untreated polypropylene pieces wereglued together using "Super Glue." These pieces were also pulled aparteasily. Polyethylene samples treated as in Example 3 were glued togetherusing "Super Glue." These samples could not be pulled apart.Polypropylene samples treated as in Example 3 were glued together using"Super Glue." These samples could not be pulled apart.

EXAMPLE 5

Polyethylene and polypropylene samples were treated as in Example 3. Thesamples were then coated with a polyurethane oil gloss black enamel oran acrylic latex gloss black enamel. The test methods as described inExample 1 were used. For the polyurethane based paint, visual inspectionrevealed that adhesion of treated samples was significantly improved forboth the polyethylene and polypropylene samples over that of theuntreated samples. For the latex based paint, adhesion of treatedsamples was significantly improved, especially in the polyethylenesamples, over that of the untreated samples. However, adhesion of thelatex paint was worse than that of the polyurethane paint.

EXAMPLE 6

A solution was prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite wasmaintained in an aqueous solution at a concentration between about 2.6%and about 5.25% by volume. The acetic anhydride was maintained in theaqueous solution at a concentration between about 0.26% and 0.53% byvolume. The solution was heated to about 60° C., and a toy boat formedfrom polyethylene was immersed in the heated solution for approximatelytwo hours. The toy boat was then painted with a base coat of RUST-OLEUMPremium Auto Primer--Fast Drying Formula. Several different paints werethen coated over this base coat. The boat was then subjected to repeatedabuse during children's bath time. After approximately 30 baths, thepaint was being stripped from primer as much as primer was beingstripped from the surface of the toy boat, as determined by the ASTMD3359-78 cross-hatch method defined in Example 1.

EXAMPLE 7

A solution is prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite ismaintained in an aqueous solution at a concentration between about 0.25%and 25% by volume. The acetic anhydride is maintained in the aqueoussolution at a concentration between about 0.01% and 5.0% by volume. Thesolution is heated at or near boiling, and a toy boat formed frompolyethylene is immersed in the heated solution for approximately onehour. The toy boat is then painted with a base coat of RUST-OLEUMPremium Auto Primer--Fast Drying Formula. Several different paints arethen coated over this base coat. The boat is then subjected to repeatedabuse during children's bath time. After approximately 30 baths, thepaint is being stripped from primer as much as primer is being strippedfrom the surface of the toy boat, as determined by the ASTM D3359-78cross-hatch method defined in Example 1.

EXAMPLE 8

A solution is prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite ismaintained in an aqueous solution at a concentration between about 0.5%and about 5.25% by volume. The acetic anhydride is maintained in theaqueous solution at a concentration between about 0.05% and 0.53% byvolume. The solution is heated at or near boiling, and a toy boat formedfrom polyethylene is immersed in the heated solution for approximatelyone hour. The toy boat is then painted with a base coat of RUST-OLEUMPremium Auto Primer--Fast Drying Formula. Several different paints arethen coated over this base coat. The boat is then subjected to repeatedabuse during children's bath time. After approximately 30 baths, thepaint is being stripped from primer as much as primer is being strippedfrom the surface of the toy boat, as determined by the ASTM D3359-78cross-hatch method defined in Example 1.

EXAMPLE 9

A solution was prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite wasmaintained in an aqueous solution at a concentration of about 2.62% byvolume. The acetic anhydride was maintained in the aqueous solution at aconcentration of about 0.4% by volume. The solution was heated to about60° C., and twelve pieces of polyethylene were immersed in the heatedsolution for approximately two hours. The treated pieces were paintedwith RUST-OLEUM Gloss Protective Spray Enamel, Gloss Black 7779. Thepainted pieces were suspended from the upper rack of a dishwasher andrun through 50 cycles on the "pots and pans" setting. Little to no lossin adhesion was noted, as determined by the ASTM D3359-78 cross-hatchmethod defined in Example 1.

EXAMPLE 10

A solution is prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite ismaintained in an aqueous solution at a concentration of about 2.62% byvolume. The acetic anhydride is maintained in the aqueous solution at aconcentration of about 0.4% by volume. The solution is heated to about60° C., and twelve pieces of polyethylene are immersed in the heatedsolution for approximately two hours. The treated pieces are paintedwith RUST-OLEUM Gloss Protective Spray Enamel, Gloss Black 7779. Thepainted pieces are suspended from the upper rack of a dishwasher and runthrough 100 cycles on the "pots and pans" setting. Little to no loss inadhesion is noted, as determined by the ASTM D3359-78 cross-hatch methoddefined in Example 1.

EXAMPLE 11

Approximately 1.25 inch by 1.25 inch squares of high densitypolyethylene (HDPE) were chosen as samples, which samples were formed byinjection molding, as described in Example 1. A side by side small scaleproduction run using the HDPE samples compared the use of oxalic acid(specifically, oxalic acid dihydrate, (HO₂ C)₂.2H₂ O) versus aceticanhydride as the activating agent. Two treatment baths were set up. Bath#1 contained 50 mLs of CLOROX bleach, 50 mLs of water; and Bath #2contained 50 mLs of CLOROX bleach, 50 mLs of water. Both baths wereheated to approximately 70° C. 1 mL of acetic anhydride was then addedto Bath #1; and 1 gram of oxalic acid dihydrate was added to Bath #2.The runs varied from 1 to 1.5 hours, and averaged 12 pieces ofpolyethylene treated per run per bath. The sample pieces were thenpainted with 2 coats of RUST-OLEUM Gloss Protective Spray Enamel, GlossBlack 7779. The treatment baths were considered to be exhausted (ie. themaximum number of sample pieces had been treated) when subsequentpainting and testing of sample pieces revealed that approximately 40% ofthe paint could be removed using the ASTM variant test method as definedin Example 1. The drop of adhesiveness to paint was generally sudden.The results were as follows:

    ______________________________________                                        Parameter         Bath # 1 Bath # 2                                           ______________________________________                                        Total # of Pieces Treated                                                                       37       48                                                 Cost of Materials (¢)*                                                                     2.9      3.1                                                Cost per Square Foot (¢)*                                                                  3.6      3.0                                                ______________________________________                                         *The cost did not include heat or water. The acetic anhydride amd oxalic      acid were priced in a 1996-97 Aldrich Chemical Company catalog.          

Oxalic acid was able to treat a greater number of parts at a reducedcost.

EXAMPLE 12

Approximately 1.25 inch by 1.25 inch squares of high densitypolyethylene (HDPE) were chosen as samples. The HDPE samples wereprocessed by structural foam injection molding, as described inExample 1. The effectiveness of bath regeneration was examined. The bathwas considered operative until subsequent painting (with 2 coats ofRUST-OLEUM Gloss Protective Spray Enamel, Gloss Black 7779) and testingof sample pieces revealed a drop of adhesiveness to paint (using theASTM variant method defined in Example 1) of approximately 50% from astarting adhesiveness of >98% as measured qualitatively by visualinspection. The drop was generally sudden. The maximum number of pieces(and number of runs) treated prior to bath failure is indicated in thefollowing table.

    ______________________________________                                                            Temp.     Time per                                                                              # Pieces                                Experiment                                                                            Formulation (RT or ° C.)                                                                     run (hours)                                                                           (runs)                                  ______________________________________                                        A       glass container                                                                           RT        5       42                                              25 mLs bleach                  (3 runs)                                       60 mLs H.sub.2 O                                                               1 mL Ac.sub.2 O.sup.1                                                B       HDPE container                                                                            RT        5       16                                              25 mLs bleach                 (1 run)                                         60 mLs H.sub.2 O                                                               1 mL Ac.sub.2 O                                                      C       aluminum liner                                                                            RT        5       15                                              25 mLs bleach                 (1 run)                                         60 mLs H.sub.2 O                                                               1 mL Ac.sub.2 O                                                      .sup. D.sup.2                                                                         glass container                                                                           50-55     2       168                                             37 mLs bleach                 (12 runs)                                       37 mLs H.sub.2 O                                                               5 mL Ac.sub.2 O                                                      ______________________________________                                         .sup.1 acetic anhydride                                                       .sup.2 This bath was regenerated between each run with 9 mLs bleach and 1     mL acetic anhydride. Results from this bath were far better than with any     previous baths.                                                          

The cost of reagents was $1.29 for 1 gallon of CLOROX bleach and $11.02per kg of Ac₂ O (Aldrich Chemical Company, 1997 Catalog). The edges ofthe samples examined were significantly wide but not included in thefollowing analysis.

In Experiment A, the cost of treatment (not including water) was 1.31¢per square foot. That would be equivalent to 84¢ to treat both sides ofa 4×8 sheet. (It is believed that 6 to 7 hours per run would have beenoptimal).

In Experiment D, the cost of treatment (not including heat or water) was5.18¢ per square foot. That would be equivalent to $3.32 to treat bothsides of a 4×8 sheet.

EXAMPLE 13

A solution was prepared as in Example 6, and was heated to about 60° C.Approximately 1.25 inch by 1.25 inch squares of high densitypolyethylene (HDPE) (formed by injection molding as described inExample 1) were immersed in the solution for 2 hours. The treatedsamples were then painted with RUST-OLEUM Premium Auto Primer--FastDrying Formula; and then 4 coats of SHERWIN WILLIAMS Prep Rite, ProBlock--Interior/Exterior Primer Sealer (White 600-6266, B51-W20).Excellent paint adhesion was noted upon visual inspection, as determinedusing the test methods described in Example 1.

EXAMPLE 14

A solution was prepared containing 80 mLs CLOROX bleach; and 5 mLsacetic anhydride. Approximately 1.25 inch by 1.25 inch squares of highdensity polyethylene (HDPE) (formed by injection molding as described inExample 1) were boiled in the solution for 2 minutes. Greater than 99%paint adhesion was noted upon visual inspection, as determined using thetest methods described in Example 1.

EXAMPLE 15

A solution is prepared comprising a sodium hypochlorite oxidizing agentand an acetic anhydride activating agent. The sodium hypochlorite ismaintained in an aqueous solution at a concentration between about 2.6%and about 5.25% by volume. The acetic anhydride is maintained in theaqueous solution at a concentration between about 0.26% and 0.53% byvolume. A toy boat is formed from at least one of, or a mixture of thefollowing polymers: polyethylene, polypropylene, polystyrene,polyisobutylene, polyvinyl chloride, polyacrylonitrile, polymethylacrylate, polymethyl methacrylate, polytetrafluoroethylene,polyformaldehyde, polyacetaldehyde, polyisoprene, polyethyleneterephthalate, polyamides, polyesters, polyurethanes, polysiloxanes,polyphenolformaldehydes, ureaformaldehydes, melamine formaldehydes,celluloses, polysulfides, polyacetates, polycarbonates, thermoplasticelastomers, ABS, and SAN. The boat is boiled in the solution for aboutone hour, and is then painted with a base coat of RUST-OLEUM PremiumAuto Primer--Fast Drying Formula. Several different paints are thencoated over this base coat. The boat is then subjected to repeated abuseduring children's bath time. After approximately 30 baths, the paint isbeing stripped from primer as much as primer is being stripped from thesurface of the toy boat, as determined by the ASTM D3359-78 cross-hatchmethod defined in Example 1.

EXAMPLE 16

Previously unpaintable polyethylene pieces were treated in baths andunder conditions listed in the "Screen Test Summary" Table below. Aftertreatment, the polyethylene pieces were rinsed with tap water, paintedwith Enterprise polyurethane paint, and allowed to dry at 91° C. for 4hours. The thus treated and painted pieces were then subjected torigorous paint adhesion testing, wherein the pieces were threedimensionally cross hatched and subjected to repeated tape pulls in thesame location, using 3M Scotch 898 Tape, commercially available fromMinnesota Mining and Manufacturing, Inc. in Minneapolis, Minn. This is areinforced tape, 1 inch wide. "P" designates pass; and "ave/pull"designates average amount of paint removed per pull. It was noted that,when paint was removed, it was only at areas on the test pieces whichhad been adjacent the "gates" of the mold apparatus. Thus, it isbelieved, since the polymer at those "gate" areas does not generally setup correctly, these "failures" are not a result of the present inventivemethod.

    ______________________________________                                        SCREEN TEST SUMMARY                                                           Panel                                                                         Designation                                                                           1     2     3   4    5    ave/pull                                                                            Conditions/Solution                   ______________________________________                                        A       P     P     P   P    P    0.0%  Boiling                               B       P     P     P   P    P    0.0%  1 min. treatment                      C       P     2%    5%  7%   10%  2.0%  750 mls bleach                        D       P     P     P   P    P    0.0%  250 mls a solution                    E       P     P     P   P    P    0.0%  of: 10 mls of 99%                                                             acetic acid in 240                                                            mls distilled H.sub.2 O               F       P     P     P   P    P    0.0%  Boiling                               G       P     4%    8%  10%  12%  2.4%  1 min. treatment                      H       P     P     P   P    P    0.0%  750 mls bleach                        I       P     2%    --  4%   4%   0.8%  250 mls vinegar                       J       P     P     P   P    P    0.0%  (4% acidity)                          K       P     5%    8%  12%  13%  2.6%  80° C.                         L       P     P     P   P    P    0.0%  1 min. treatment                                                              1000 mls bleach                                                               10 mls 99% acetic                                                             acid                                  M       P     P     P   P    1%   0.2%  50° C.                         N       P     2%    --  --   2%   0.4%  1 min. treatment                                                              1000 mls bleach                                                               10 mls 99% acetic                                                             acid                                  O       P     P     P   P    P    0.0%  boiling                               P       P     P     P   1%   1%   0.2%  1 min. treatment                      Q       P     P     P   P    P    0.0%  1000 mls bleach                                                               10 mls 99% acetic                                                             acid                                  ______________________________________                                    

EXAMPLE 17

"Unpaintable" modified polyolefin. A solution was prepared by bringing 6L of a standard bleach solution commercially available from the CloroxCompany under the trademark CLOROX (5.25% sodium hypochlorite) to 80° C.and adding 300 mLs of acetic anhydride. There was much gas evolution.The temperature of the bath was raised to 88° C. Over a period of 15seconds, approximately 4 pounds of a powdered unpaintable grade ofautomotive polypropylene-based polyolefin was added. The polyolefinpowder was a proprietary polypropylene based homopolymer made by Equistaand compounded by A. Schulman, Inc., located in Akron, Ohio. Although nomesh size information was provided, the particles appeared to range insize from talc to salt grain. This low density polyolefin floated andwas stirred slowly, pushing it under the solution. After approximately 7minutes, it appeared that the polyolefin was exhibiting good wetting.The process of repeatedly pushing the polyolefin under the solution wascontinued. After a total of 15 minutes had passed, the polyolefin andsolution were poured into approximately 6 L of cold tap water. Thepolyolefin and 12 L of solution were then poured through a sheet linedstrainer. The polyolefin was rinsed repeatedly with cold water until noodor from the treatment solution was detected. Upon visible inspection,the powder exhibited less static properties and appeared somewhat"stickier," thereby signalling that the powder had been treatedaccording to the present invention.

The treated polyolefin is molded into test cards and examined for paintadhesion and physical properties. It is found that improved paintadhesion is imparted on the test cards prepared from the treatedpolyolefin, as determined by the ASTM D3359-78 cross-hatch methoddefined in Example 1. The physical properties are also improved.

EXAMPLE 18

Polyolefin held submerged. A solution is prepared as in Example 17.Another 4 pounds of the polyolefin powder as used in Example 17 is addedand is held submerged with mixing, thereby allowing the apparent wettingto be achieved within 1 minute. The treated polyolefin powder is rinsedas described in Example 17.

The treated polyolefin is molded into test cards and examined for paintadhesion and physical properties. It is found that improved paintadhesion is imparted on the test cards prepared from the treatedpolyolefin, as determined by the ASTM D3359-78 cross-hatch methoddefined in Example 1. The physical properties are also improved.

EXAMPLE 19

Replacement of polyolefin with HDPE. A solution is prepared as inExample 17. 4 pounds of unmodified high density polyethylene (HDPE)powder is held submerged with mixing, thereby allowing the apparentwetting to be achieved within 2 minutes. The treated powder is rinsed asin Example 17.

The treated polyolefin is molded into test cards and examined for paintadhesion and physical properties. It is found that improved paintadhesion is imparted on the test cards prepared from the treatedpolyolefin, as determined by the ASTM D3359-78 cross-hatch methoddefined in Example 1. The physical properties are also improved.

EXAMPLE 20

Polyolefin flake instead of powder. A solution is prepared as in Example17. 4 pounds of polypropylene or polyethylene flake is held submergedwith mixing, thereby allowing the apparent wetting to be achieved within2 minutes. The treated flake is rinsed as in Example 17.

The treated polypropylene or polyethylene flake is molded into testcards and examined for paint adhesion and physical properties. It isfound that improved paint adhesion is imparted on the test cardsprepared from the treated polyolefin, as determined by the ASTM D3359-78cross-hatch method defined in Example 1. The physical properties arealso improved.

EXAMPLE 21

Spray application. The solution of Example 17 is prepared at the exit ofa heated spray gun nozzle. The solution is raised to 100° C. and isapplied to powdered or flaked polypropylene or polyethylene material.The hot solution is applied throughout a period of 1 minute.

The treated polyolefin powder or flake is molded into test cards andexamined for paint adhesion and physical properties. It is found thatimproved paint adhesion is imparted on the test cards prepared from thetreated polyolefin or flake, as determined by the ASTMD3359-78,cross-hatch method defined in Example 1. The physicalproperties are also improved.

EXAMPLE 22

Hot vapor application. The solution in Example 17 is prepared and flashheated to form a reactive vapor. A structural article formed from aconventionally unpaintable polypropylene or polyethylene material isexposed to the reactive vapor for 2 minutes. The article is examined forpaint adhesion. It is found that improved paint adhesion is imparted onthe article treated with the reactive vapor, as determined by the ASTMD3359-78 cross-hatch method defined in Example 1.

EXAMPLE 23

NaOCl and OA added directly to the press. Solid sodium hypochlorite andoxalic acid are added directly at the mouth of an injection moldingpress. The sodium hypochlorite is maintained at a concentration of 0.5%to 5% relative to the polypropylene or polyethylene being processed. Theoxalic acid is maintained at a concentration of 0.25% to 5% relative tothe polyolefin. The polyolefin is then injection molded into astructural component. The component is examined for paint adhesion. Itis found that improved paint adhesion is imparted on the component, asdetermined by the ASTM D3359-78 cross-hatch method defined in Example 1.

EXAMPLE 24

Use of solid reagents in conjunction with fillers. Solid sodiumhypochlorite, oxalic acid, and a filler (calcium carbonate) are addeddirectly at the mouth of an injection molding press. The sodiumhypochlorite is maintained at a concentration of 0.5% to 5% relative tothe polyolefin being processed. The oxalic acid is maintained at aconcentration of 0.25% to 5% relative to the polyolefin. The filler ismaintained at a concentration between 2% and 20% relative to thepolyolefin. After processing the polyolefin into a structural component,it is found that the component exhibits greatly improved adhesion andphysical properties.

EXAMPLE 25

Treatment inside a tool. The inner core of a tool of an injectionmolding press is sprayed with the solution prepared in Example 17 orwith a suspension of the solid reagent(s) described in Examples 23 or24. Upon injection of the polyolefin into the tool, the surface of thestructural component is made adhesive as it conforms to the inside ofthe tool.

EXAMPLE 26

Hot vapor inside a tool. The solution in Example 17 is prepared andflash heated to a reactive vapor. The vapor is forced into a tool thatis almost closed. When the polyolefin is injected into the tool, thesurface is treated, thereby rendering the structural component adhesive.The physical properties are also improved.

While preferred embodiments, forms and arrangements of parts of theinvention have been described in detail, it will be apparent to thoseskilled in the art that the disclosed embodiments may be modified.Therefore, the foregoing description is to be considered exemplaryrather than limiting, and the true scope of the invention is thatdefined in the following claims.

What is claimed is:
 1. A method for improving adhesion characteristicsof a polymeric material, comprising the steps of:contacting thepolymeric material with a composition containing at least one oxidizingagent, said oxidizing agent present in a kinetically degrading statewhich produces at least one chemical intermediate reactive with thepolymeric substrate in a controlled reaction mechanism; and maintainingcontact between the polymeric material and the composition for aninterval sufficient to impart functional groups derived from saidoxidizing agent into the polymeric material; reacting said oxidizingagent with an activating agent which preferentially reacts with saidoxidizing agent to produce said at least one intermediate reactive withthe polymeric substrate, said activating agent selected from the groupconsisting of carboxylic acids, anhydride derivatives of carboxylicacids, acid halide derivatives of carboxylic acids, sulfonic acidderivatives of carboxylic acids, selenic acid derivatives of carboxylicacids, perchloric acid derivatives of carboxylic acid, boric acidderivatives of carboxylic acid, dicarboxylic acid, anhydride derivativesof dicarboxylic acid, acid halide derivatives of dicarboxylic acid,sulfonic acid derivatives of dicarboxylic acids, selenic acidderivatives of dicarboxylic acid, perchloric acid derivatives ofdicarboxylic acid, boric acid derivatives of dicarboxylic acid,synthetic equivalents thereof, and mixtures thereof; wherein saidreacting step in which said oxidizing agent is reacted with saidactivating agent occurs in at least one of: an aqueous environment; ananhydrous environment; and a vaporous environment; wherein the reactionbetween said oxidizing agent and said activating agent occurs at a rateessentially equal to reaction between said polymeric substrate and thereaction intermediate; and wherein said oxidizing agent is a bivalentoxygen compound selected from the group consisting of oxycompounds ofchlorine, oxycompounds of bromine, oxycompounds of iodine, oxycompoundsof boron, oxycompounds of nitrogen and mixtures thereof.
 2. The methodof claim 1 wherein said bivalent oxygen compound is selected from thegroup consisting of:oxycompounds of chlorine selected from the groupconsisting of hypochlorous acid, alkali metal salts of hypochlorous acidand hydrates thereof, alkaline earth metal salts of hypochlorous acidand hydrates thereof, perchloric acid, alkali metal salts of perchloricacid and hydrates thereof, chloric acid, alkali metal salts of chloricacid and hydrates thereof, alkaline earth metal salts of chloric acidand hydrates thereof; oxycompounds of bromine selected from the groupconsisting of hypobromous acid, alkali metal salts of hypobromous acidand hydrates thereof, alkaline earth metal salts of hypobromous acid andhydrates thereof, bromic acid, alkali and alkaline earth metal salts ofbromic acid and hydrates thereof; oxycompounds of iodine selected fromthe group consisting of iodic acid, alkali and alkaline earth metalsalts of iodic acid and hydrates thereof, periodic acid, alkali andalkaline earth metal salts of periodic acid and hydrates thereof;oxycompounds of boron selected from the group consisting of boric acid,alkaline earth and alkali metal salts and hydrates thereof, alkaliperborates and hydrates thereof, alkaline earth metal perborates andhydrates thereof; oxycompounds of nitrogen selected from the groupconsisting of nitric acid, alkali and alkaline earth metal salts ofnitric acid and hydrates thereof; and mixtures thereof.
 3. The method ofclaim 1 wherein the carboxylic acid has the general formula: ##STR12##wherein x and y are integers between 0 and 20 inclusive, with the sum ofx and y being an integer of 20 or less, wherein R is a functionalityselected from the group consisting of substituted or unsubstitutedaromatic hydrocarbon groups, branched or unbranched alkyl groups, thealkyl group having between 1 and 27 carbon atoms, and mixtures thereof,and wherein each variable R', R", R'" and R"" is a functionalityselected from the group consisting of hydrogen, amines, hydroxyl,phenyl, phenol radicals, and mixtures thereof, each of theabove-mentioned R variable functionalities being chosen independently ofthe other R variable functionalities, and wherein R" may also beselected from the group consisting of anhydrides, halide salts, selenicacid salts, perchloric acid salts, boric acid salts, and mixturesthereof; andwherein the dicarboxylic acid has the general formula:##STR13## wherein x is an integer between 1 and 20 inclusive and R andR' are functionalities selected from the group consisting of hydrogen,hydroxyl radicals, amines, phenyl radicals and mixtures thereof.
 4. Themethod of claim 3 wherein said contacting step occurs at a temperaturebetween about 20° C. and a temperature at which decomposition of thepolymeric material commences.
 5. The method of claim 4 wherein thepolymeric material is selected from the group consisting of:additionpolymers selected from the group consisting of polyethylene,polypropylene, polystyrene, polyisobutylene, polyvinyl chloride,polyacrylonitrile, polymethyl acrylate, polymethyl methacrylate,polytetrafluoroethylene, polyformaldehyde, polyacetaldehyde,polyisoprene, and mixtures thereof; condensation polymers selected fromthe group consisting of polyamides, polyesters, polyurethanes,polysiloxanes, polyphenolformaldehydes, ureaformaldehydes, melamineformaldehydes, celluloses, polysulfides, polyacetates, polycarbonates,and mixtures thereof; thermoplastic elastomers selected from the groupconsisting of styrene-isoprene-styrene, styrene-butadiene-styrene,copolyesters, copolyester ethers, silicone-polyamides,silicone-polyesters, silicone-polyolefins, silicone-styrenes, aromaticpolyether-urethanes, alpha cellulose filled ureas, polyvinylchloride-acetates, vinylbutyrals, and mixtures thereof; co-polymersselected from the group consisting of polyester-polyethers,polyether-polysiloxanes, polysiloxane-polyamides, polyesteramides,copolyamides, nylons, and mixtures thereof; and mixtures thereof.
 6. Themethod of claim 5 wherein the polymeric material is selected from thegroup consisting of polyethylenes, polypropylenes, polyesters,thermoplastic elastomers, and mixtures thereof.
 7. The method of claim 6wherein the polymeric material is a polyester selected from the groupconsisting of polybutylene terephthalate, polyethylene terephthalate,and mixtures thereof.
 8. The method of claim 3 wherein the reactionbetween said oxidizing agent and said activating agent occurs at a rateessentially equal to reaction between said polymeric substrate and thereaction intermediate.
 9. The method of claim 3 wherein the oxidizingagent is maintained in an aqueous solution at a concentration betweenabout 0.25% and 25% by volume, and wherein the activating agent ismaintained in said aqueous solution at a concentration between about0.01% and 5.00% by volume.
 10. The method of claim 1 wherein thepolymeric material is a virgin polymeric material.
 11. The method ofclaim 1 wherein the contacting step is carried out by spraying thecomposition onto at least one of a virgin polymeric material and apolymeric substrate with a heated spray gun.
 12. The method of claim 1wherein the composition is flash heated to form a reactive vapor, andthe contacting step is carried out by exposing a polymeric substrate tothe vapor for a period of time sufficient to render the substrateadhesive.
 13. The method of claim 3 wherein the oxidizing agent and theactivating agent are each in solid form, and wherein the method furthercomprises the step of placing the solid agents at the mouth of aninjection molding press, wherein the contacting step occurs duringmolding of a virgin polymeric material into a polymeric substrate. 14.The method of claim 3 wherein the composition takes the form of at leastone of: the oxidizing agent and the activating agent are each in solidform held in a suspension; and the oxidizing agent and the activatingagent are in an aqueous solution; and wherein the method furthercomprises the step of spraying the composition onto the inner core of atool of an injection molding press, wherein the contacting step occursduring molding of a virgin polymeric material into a polymericsubstrate.
 15. The method of claim 3 wherein the composition is flashheated to form a reactive vapor, and wherein the vapor is forced into amolding tool substantially immediately before closing the tool, whereinthe contacting step occurs during molding of a virgin polymeric materialinto a polymeric substrate.
 16. The method of claim 3 wherein theactivating agent is selected from the group consisting of aceticanhydride, glacial acetic acid, vinegar, oxalic acid, formic acid, andmixtures thereof.
 17. The method of claim 3 wherein the oxidizing agentis selected from the group consisting of sodium hypochlorite, calciumhypochlorite, calcium hypochlorite tetrahydrate, and mixtures thereof.18. A method for improving adhesion characteristics of a polymericmaterial, comprising the steps of:contacting the polymeric material witha composition containing at least one oxidizing agent, said oxidizingagent present in a kinetically degrading state which produces at leastone chemical intermediate reactive with the polymeric substrate in acontrolled reaction mechanism; maintaining contact between the polymericmaterial and the composition for an interval sufficient to impartfunctional groups derived from said oxidizing agent into the polymericmaterial; and reacting said oxidizing agent with an activating agentwhich preferentially reacts with said oxidizing agent to produce said atleast one intermediate reactive with the polymeric substrate; whereinsaid oxidizing agent is a bivalent oxygen compound selected from thegroup consisting of oxycompounds of chlorine, oxycompounds of bromine,oxycompounds of iodine, oxycompounds of boron, oxycompounds of nitrogenand mixtures thereof; and wherein said activating agent is selected fromthe group consisting of carboxylic acids, anhydride derivatives ofcarboxylic acids, acid halide derivatives of carboxylic acids, sulfonicacid derivatives of carboxylic acids, selenic acid derivatives ofcarboxylic acids, perchloric acid derivatives of carboxylic acid, boricacid derivatives of carboxylic acid, dicarboxylic acid, anhydridederivatives of dicarboxylic acid, acid halide derivatives ofdicarboxylic acid, sulfonic acid derivatives of dicarboxylic acids,selenic acid derivatives of dicarboxylic acid, perchloric acidderivatives of dicarboxylic acid, boric acid derivatives of dicarboxylicacid, synthetic equivalents thereof, and mixtures thereof.
 19. Themethod of claim 18 wherein the activating agent is selected from thegroup consisting of acetic anhydride, glacial acetic acid, vinegar,oxalic acid, formic acid, and mixtures thereof.
 20. The method of claim19 wherein the oxidizing agent is selected from the group consisting ofsodium hypochlorite, calcium hypochlorite, calcium hypochloritetetrahydrate, and mixtures thereof.